The invention relates to an arrangement for the variable control of the valves of an internal combustion engine including separate intake valve operating camshafts for opening and closing the intake valves and means for changing the phase relation between the two intake valve operating camshafts.
Such an arrangement is known for example from DE 196 00 536 A1. With such an arrangement, the exhaust gas emissions of an engine can be reduced and its torque can be increased. Also, the engine charge change losses and, as a result, the fuel consumption of the engine can be reduced. Furthermore, the engine can be controlled without a throttle valve in the air intake duct.
The arrangement includes two camshafts, a first one for controlling the exhaust valve and the opening of the intake valves and a second camshaft for controlling the closing of the intake valves. The intake cams for operating the intake valves include for each intake valve an intake valve opening cam on the first cam shaft and an intake valve closing cam on second camshaft which operate in an additive fashion. The control movement of the intake cams is transmitted to the intake valves by way of intake valve control levers. The control movement of the exhaust cams is transmitted to the exhaust valves by way of exhaust valve control levers. By means of an arrangement for changing the phase relation between the two camshafts the relative angle of rotation of the two camshafts can be changed so as to affect the opening movement and the opening duration of the intake valve.
The exhaust valve cams and the intake valve opening cams are arranged on the first camshaft axially one after the other so that at least one of the cams is arranged spaced from a plane extending normal to the camshaft and including the axis of one of the valves. The distance between the cam and the valve is bridged by a transmission lever. As a result, the contact point between the respective cam and the transmission lever is disposed outside the plane of movement of the transmission lever. Such an asymmetry, however, generates torque forces which may lead to early wear and which may detrimentally affect an accurate motion transmission.
It is the object of the present invention to provide an arrangement for the variable control of the valves of an internal combustion engine which operates highly reliably and which takes up only a relatively small space on the cylinder head.